Question 2: They are created when ________ reaches the surface but, as there is a large difference in temperature between the lava and the water, the surface of the emergent tongue cools very quickly, forming a skin.

Question 3: The presence of pillow lavas in the oldest preserved volcanic sequences on earth, the Isua and Barbertongreenstone belts, confirms the presence of large bodies of water on the Earth's surface early in the ________.